Hydrometallurgical beneficiation of ilmenite

[摘要] English: The aim of this project was to investigate the dissolution and possible separation of Ti and Fe in ilmenite using eco-friendly and economically viable procedures. Method validation was established with commercial salts such as FeCl3·6H2O and TiCl3 including Ti and Fe metal powders with high purity. The successful procedures were evaluated for the dissolution of ilmenite and subsequent separations of Ti and Fe in the mineral matrix. Dissolution techniques such as open-beaker acid digestion and flux fusion were evaluated. The separation techniques which were investigated include selective precipitation, solvent extraction and ion exchange. Analytical determinations were performed with inductively coupled plasma-optical emission spectroscopy (ICP- OES) while infrared spectroscopic (IR) analyses was used to characterize the Ti and Fe containing compounds.Acid dissolution was investigated with different mineral acids which included aqua regia, HCl, HNO3, H2SO4 and H3PO4. Analytical results showed good average recoveries ranging from 98(1) to 105.2(2) % Ti in TiCl3 and 100(4) to 103(2) % Fe in FeCl3·6H2O after these salts were dissolved in water. The dissolution of the Ti and Fe metal powders was investigated with aqua regia, HCl, HNO3, H2SO4 and H3PO4 and only H2SO4 and H3PO4 successfully dissolves the metal powders and excellent Ti and Fe recoveries of 103.6(5) and 105.2(6) % Ti with 103(2) and 103(2) % Fe were obtained.The dissolution of ilmenite with acid digestion yielded 38.39 % TiO2 and 45.25 % Fe2O3 with H2SO4 and 34.79 % TiO2 and 19.50 % Fe2O3 in H3PO4 with clearly pointed to incomplete sample dissolution. Flux fusion using NH4·HF2, KF, K2S2O7, Na2CO3, LiBO2, Na2B4O7 and phosphate mixture (Na2HPO4/NaH2PO4·H2O) as fluxes was also investigated. Only the borates (LiBO2 and Na2B4O7) and the phosphate flux mixture (Na2HPO4/NaH2PO4·H2O) indicated complete ilmenite dissolution.The quantitative results obtained after the flux fusion method (borates and phosphate), were compared with the non-destructive SEM-EDS semi-quantitative results. Comparative results were obtained for Ti, Mg, Mn and Al with some difference observed in the Fe quantities that were recovered.The separation of Ti and Fe in the ilmenite was further investigated using only the phosphate flux method. Selective precipitation using NaTPB/phenantroline was unsuccessful with both Ti and Fe precipitated in solution. However the use of only NaPT resulted in the complete precipitation of Fe (99.60(1) %) while Ti remained in solution (103(1) %). Separation using solvent extraction indicated that Fe was preferentially isolated with 100 % Fe and 0.00 % Ti and thus achieving a complete separation using NaPT in different organic solvents. Separation of Fe and Ti using the MIBK/NaPT and 1-octanol/NaPT combinations indicated a selective extraction of Fe into the MIBK and 1- octanol with 95.9(3) to 103(3) % Fe and 0.0 to 24(9) % Ti obtained in the organic phase using HCl, H2SO4 and H3PO4, depending on the acid concentrations. Separation factors were calculated to in the range of 1.7 to 8.6 x 107. Solvent extraction using kerosene/TOPO and MIBK/acacH systems indicated a selective extraction of Fe into the organic phase (0.8(1) to 22(6) % Ti and 2(2) to 99.0(8) % Fe in kerosene, 0.7(2) to 7(2) % Ti and 22.5(2) to 100(2) % Fe in MIBK) with separation factors of 1.4 x 102 to 3.3 x 105 in kerosene and 23 x 100 to 1.6 x 105 in MIBK in HCl matrix.The separation of Ti and Fe with strong and weak basic ion exchange resins (Amberlite IRA-900, Amberlite IRA 402, Dowex 1x4 ion exchange resin, weak basic Dowex Marathon WBA and Dowex 66 free base) indicated the successful separations with Ti the strongly retained species during elution with H3PO4 solution. Fe recoveries of 96(1) to 103.46(1) % were obtained for the weak anionic resins using 3.0 and 5.0 M H3PO4 as eluent. The strongly retained Ti was eluted with 5.0 M HCl with recoveries of 99.1(1) to 103(4) %. Recoveries were generally poor with the use of strong anionic exchange resins for both Fe and Ti resins (62(2) to 74(5) % for Fe and 68(4) to 84(3) % for Ti). The separation factor (α) for strong and weak anionic resins were in the range of 1.4 (Fe/Ti) to 6.7 (Fe/Ti) in 3.0 to 10.0 M H3PO4.

[发布机构] University of the Free State